Coupled Ocean-Ice-Atmosphere Variability and Change in the Nordic Seas

Bennett, Miriam Gwenda (2026) Coupled Ocean-Ice-Atmosphere Variability and Change in the Nordic Seas. Doctoral thesis, University of East Anglia.

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Abstract

The Nordic Seas form a critical interface between the Arctic and North Atlantic, mediating exchanges of heat, freshwater and dense water that influence the Atlantic Meridional Overturning Circulation. Rapid climate change is modifying sea-ice cover, boundary current pathways and upper-ocean stratification, with implications for high-latitude ocean-atmosphere coupling and water mass transformation. This thesis examines how these processes vary in the present climate and how they respond to strong anthropogenic forcing.

Observations and reanalysis data are used to investigate historic spatiotemporal variability in sea-ice conditions and upper-ocean structure along the north-east Greenland margin. Variability in the Northeast Water Polynya is shown to be primarily controlled by atmospheric circulation, while concurrent ocean changes reveal widespread warming, surface freshening and subsurface salinification, consistent with enhanced ice melt and evolving stratification.

The physical oceanography of the wider Nordic Seas is explored using the HadGEM3 global coupled climate model at low, medium and high-resolution, and the simulated diagnostics are evaluated against observation-based products. The low-resolution model does not accurately resolve the complex ocean system, while the medium-resolution has muted variability and dynamics. However, despite biases in boundary current strength, the high-resolution simulation reproduces the large-scale circulation, seasonal cycle and key hydrographic contrasts well, providing confidence in its projected response. Under a high-emissions scenario, increased inflow of Atlantic-origin water intensifies warming and salinification along boundary currents, strengthening horizontal density gradients and altering mixed layer depths.

The high-resolution future projections show a decline in dense water formation driven by rising ocean temperatures, reduced brine rejection and a poleward shift in surface-forced transformation. Meanwhile, overturning circulation within the Nordic Seas strengthens and shifts poleward, while the density of overturning decreases, implying a shoaling circulation. These results highlight competing mechanisms linking sea-ice retreat, boundary current dynamics and overturning, while reinforcing the sensitivity of the Nordic Seas to climate change.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Environmental Sciences
Depositing User:	Chris White
Date Deposited:	11 Jun 2026 13:49
Last Modified:	11 Jun 2026 13:49
URI:	https://ueaeprints.uea.ac.uk/id/eprint/103377
DOI:

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